Role of mono- and biarticular muscles in explosive movements.

From 24 vertical jumps (eight subjects, three jumps each), calculations of forces, torques, and power per joint were combined with EMG data of eight leg muscles and with estimations of their contraction velocities. In the second part of the push-off, a high power output of 3000-4000 W was delivered in the ankle joints during plantar flexion. This is attributed to a sequential energy flow from hip to knee and ankle joints. Through coordinated actions of both the m. gluteus maximus and the m. rectus femoris as well as the m. vastus med., intermedius and lat. (mm. vasti) and the m. gastrocnemius, power delivered by the monoarticular extensors of the hip and knee joints was transported distally via the biarticular muscles to the ankle joints. During the high plantar flexion velocity at the end of the push-off, hip and knee joints showed high extension velocities resulting in relatively low contraction velocities for the biarticular muscles. As a consequence they could deliver high forces, which allowed them to transport energy in a proximodistal direction and allowed them to decelerate the angular velocities of the hip and knee joints without losses due to eccentric contractions. It is concluded that this power transport is essential in the execution of explosive movements.